Wouldn't the K shape only affect targeting of affluent users that are desirable to luxury brands?
Think through the net margins of the bottom of the K left to them. And then the spend against their own K economy on the business side.
Not all companies that have massive budgets only sell to affluent consumers. For example, walmart, amazon, most streaming services, coca-cola, pepsi, mcdonalds, etc.
It affects everyone. It's always been the case, also in traditional advertising. As soon as a company gets rich it defaults to massive marketing (at a loss) to stay on top and drown the underdogs. That's why I think marketing spend should be capped by revenue by law. The current system stiffles competition